The invention relates to the determination of a magnetic field using a Hall element.
As is well recognized, and as illustrated in FIG. 1, the determination of a magnetic field with a Hall element comprises the steps of passing a control current I.sub.C between a pair of input terminals or control current terminals of a Hall element 1 which is located within a magnetic field to be determined, detecting the Hall effect which results from the flux density B of the magnetic field as a Hall voltage is developed across a pair of output terminals which are disposed at right angles to the control current terminals, and determining the flux density B from the detected Hall voltage V.sub.H on the basis of a predetermined relationship between the flux density and the Hall voltage.
A Hall element has a high sensitivity and is capable of detecting a very weak magnetic field. In particular, a Hall element comprising an evaporated indium antimonide has an exceedingly high sensitivity. A Hall voltage V.sub.H of a Hall element 1 can be defined by the following expression: EQU V.sub.H = K(T)I.sub.C B (1)
wherein K(T) represents a coefficient, referred to hereafter as a temperature coefficient, which depends on the configuration of the element, temperature and the like, I.sub.C represents the control current and B the flux density which passes through the Hall element in a direction perpendicular thereto. Although a Hall element has a high sensitivity, it suffers from a strong dependency of its output on the temperature. The temperature coefficient K(T) appearing in the equation (1) varies with a change in the temperature, and the variation is particularly noticeable with the Hall element comprising evaporated indium antimonide. An exemplary variation of the temperature coefficient with temperature is graphically illustrated in FIG. 2. As a consequence, in the determination of a magnetic field with a Hall element, a variation in the magnitude of the temperature coefficient K(T) must be compensated by applying a correction or conversion to the Hall voltage V.sub.H obtained, or by maintaining the environmental temperature constant, to prevent a variation in the temperature coefficient.